Flexible film circuit carriers currently on the market are generally fabricated from polyimides or silicone polymers with copper lines as the electrical conductor. The flexible film circuit carriers are usually connected to another conductor member such as a circuit board or circuit card, for instance, for power or signal communication, by what is generally referred to as a "flat on flat" arrangement. For instance, the flexible film circuit carrier includes a flat contact pad which may be gold-plated.
The contact pad, in turn, lines up with a corresponding contact pad on the surface of, for example, the integrated circuit board to which the flexible carrier is to be contacted. The contact pad on the surface contains, for instance, gold to facilitate the subsequent mating process. However, in order to achieve adequate and reliable contact, it is necessary to employ considerable pressure or force to the substrates to be mated. Attempts to reduce the required force resulted in bonding of small metal spheres to the surface of one of the mating pads.
In addition, the prior processes require plating the entire contact pads and spheres with gold which involves significant expense, as well as engineering problems such as current distribution, relatively low yields, reworking, and the like. The need for providing the contact spheres also involves special handling which requires great care. Even with extraordinary care, problems still occur in handling of the relatively small sized gold spheres which, at times, results in the spheres being dislodged and falling into plated through-holes of the boards or cards.